The present invention relates to a coil assembly for use in a communication system. More particularly it relates to a coil assembly for use in a communication system in which the spacial orientation of the coil assembly relative to other components in the system can not be predetermined.
There exist numerous communication systems in which communication is to be established between two or more components by means of a linking magnetic field and in which at least one of the components is movable relative to another such that isotropic sensitivity is important for maintaining communication. The need for isotropic response in paging systems and article surveillance systems, to name two examples, should be readily apparent.
Assuming that communication is to be established either to or from a loop coil by means of an AC magnetic field the problem exists of ensuring adequate magnetic coupling between the coil and the field regardless of the spacial orientation of the coil relative to the lines of flux constituting the field. It is well known, for example, that a flat coil immersed in a magnetic field wherein all the lines of flux are parallel to the plane of the coil will experience little or no magnetic coupling with such field. On the other hand, if the coil is used to produce the field, the lines of flux will be oriented normal to the general plane of the coil and not parallel thereto. The action of such coil is clearly anisotropic and null conditions will exist in any communication system in which the spacial orientation of the coil can not be predetermined.